In the electrophotographic process, as commonly known, an electrostatic latent image is formed on an image carrier and the fanned latent image is developed to form a toner image. Thus formed toner image is transferred onto a recording medium such as paper.
Highly definitional expression of photographic images and patterns can be realized accompanied with increase in image quality, particularly that of color image.
However, a problem of roughening of the image, particularly at medium density portion of the image, is caused when the quality of the photographic image or pattern image is increased.
It is proposed in Patent Documents 1 and 2 for inhibiting the roughening of image to provide an electrode facing to the image carrier on the downstream side of the developing device and alternative electric voltage is applied to the electrode for reciprocally moving the toner between the image carrier and the electrode.
It is considered that the roughening of the image is caused by formation of ununiformity of the toner at the portion of the image where the toner is to be uniformly distributed. In Unexamined Japanese Patent Application Publication No. 4-372964 and Unexamined Japanese Patent Application Publication No. 6-274040, the toner distribution is made uniform by the reciprocal movement of the toner for inhibiting the roughening.